Polymer interfacial modified inorganic solid-state electrolyte, preparation method and application thereof

Abstract

The application provides a polymer interfacial modification inorganic solid-state electrolyte and a preparation method and application thereof, and relates to the field of polymer interfacial modification inorganic solid-state electrolyte. The method comprises the following steps: mixing LITFSI, PVDF-HFP, DMF, inorganic solid-state electrolyte powder and ionic liquid to obtain a PVDF-HFP-based polymer mixed solution, uniformly coating the LATP ceramic sheet solid-state electrolyte through a pressure coating method, and drying at high temperature to obtain a double-layer solid-state electrolyte; mixing LITFSI, PEO, acetonitrile and ionic liquid to obtain a PEO-based polymer mixed solution, and uniformly coating the ceramic sheet solid-state electrolyte on the other side through a pressure coating method and drying to obtain a PVDF-HFP@LATP@PEO sandwich structure solid-state electrolyte. The film can effectively inhibit the interface reaction of LATP on the lithium negative electrode side, increase the wettability of the positive and negative electrode interfaces, and meet the high-temperature and normal-temperature cycle performance requirements of the solid-state battery.

Description

Technical Field

[0001] This invention relates to the field of polymer interface modified inorganic solid electrolyte technology, and particularly to a polymer interface modified inorganic solid electrolyte, its preparation method and application. Background Technology

[0002] With the massive consumption of fossil fuels, energy and environmental pressures are increasing, making the development of new energy sources a strategic direction for alleviating or solving these problems. In the field of new energy storage, lithium-ion batteries have received widespread attention and are commonly used in smartphones, laptops, automobiles, and other fields due to their advantages such as high energy density, high output voltage, long cycle life, and low self-discharge rate. However, existing lithium-ion batteries use flammable organic liquid electrolytes and thermally shrinkable organic separators, which can lead to serious safety accidents such as fires and explosions if thermal runaway occurs. All-solid-state batteries, by their very nature, offer advantages such as safety, leak-free operation, and suppression of lithium dendrite formation, effectively replacing liquid batteries.

[0003] Solid-state electrolytes can be mainly classified into: oxide solid-state electrolytes, sulfide solid-state electrolytes, polymer solid-state electrolytes, and composite solid-state electrolytes. Sulfide solid-state electrolytes are expensive due to the use of lithium sulfide, phosphorus sulfide, and other materials. They decompose upon contact with air, producing toxic substances such as hydrogen sulfide and causing a sharp decrease in lithium-ion conductivity. They require inert gas protection throughout production and storage, making them uneconomical. Polymer solid-state electrolytes and composite solid-state electrolytes have lithium-ion conductivity 2-3 orders of magnitude lower than oxide electrolytes. Their poorer mechanical properties are insufficient to completely suppress lithium dendrite growth, potentially leading to short circuits and other extreme situations, which may cause safety problems similar to those of liquid lithium-ion batteries. Oxide solid-state electrolytes have high lithium-ion conductivity (10⁻⁶ ppm). -4 S / cm-10 -3 Solid-state electrolytes exhibit good air stability (S / cm) and require no inert atmosphere for preparation and storage, demonstrating promising development prospects. Oxide solid-state electrolytes are represented by NASICON-type (LATP, LAGP) and Garnet-type (LLZO, LLZTO, etc.) solid-state electrolytes.

[0004] Among them, LATP (lithium aluminum titanium phosphate) inorganic solid electrolyte (oxide solid electrolyte) has attracted much attention as a typical representative, with advantages such as high ionic conductivity, low preparation cost, and simple preparation process. However, due to its rigidity, it has a large interfacial impedance when directly contacting and assembling with positive and negative electrodes. During charging and discharging, lithium ions cannot smoothly pass through the positive electrode / electrolyte and electrolyte / negative electrode interfaces, which seriously affects the electrochemical performance of solid lithium batteries. At the same time, when oxide solid electrolytes come into direct contact with the highly reducing metallic lithium negative electrode, some components will be reduced, which will cause changes in the electrolyte structure and seriously reduce its lithium ion conductivity. That is, due to the Ti on the lithium negative electrode side...4+ Problems such as high impedance at the positive and negative electrode interfaces limit its application. Summary of the Invention

[0005] This invention provides a polymer interface modified inorganic solid electrolyte, its preparation method, and its application, with the aim of solving the aforementioned problems existing in the background art.

[0006] To achieve the above objectives, embodiments of the present invention provide a polymer interface-modified inorganic solid electrolyte, its preparation method, and its application.

[0007] This invention uses a pressure coating method to coat an ionic liquid-type polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and polyoxyethylene (PEO) polymer mixture onto an LATP ceramic sheet. The addition of the ionic liquid to the PVDF-HFP-based polymer effectively improves the uniformity of the inorganic ceramic powder, thereby providing better ionic conductivity, while also increasing the interfacial wettability between the positive electrode and LATP. The addition of the ionic liquid to the PEO-based polymer effectively improves the polymer's flowability and mechanical strength, increasing ionic conductivity while inhibiting direct contact between LATP and the lithium negative electrode.

[0008] One embodiment of the present invention provides a method for preparing a polymer interface-modified inorganic solid electrolyte, comprising the following steps:

[0009] S1: Li₂CO₃, Al₂O₃, TiO₂, and NH₄H₂PO₄ powders were weighed out in a molar ratio of 0.65:0.15:1.7:3, and then pre-calcined to obtain Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is ball-milled and pressed to obtain a ceramic blank, which is then sintered by embedding powder and polished to obtain LATP ceramic sheet;

[0010] S2: Take 1-3 parts by weight of inorganic solid electrolyte powder, 4-12 parts by weight of lithium bis(trifluoromethanesulfonate)imide (LITFSI), 6-18 parts by weight of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), 40-120 parts by weight of N,N-dimethylformamide (DMF), and 2-6 parts by weight of ionic liquid, mix them, and stir magnetically to obtain a PVDF-HFP based polymer mixture.

[0011] S3: The PVDF-HFP based polymer mixture is coated onto the LATP ceramic sheet by pressure coating and then dried by vacuum evaporation to obtain the PVDF-HFP@LATP bilayer solid electrolyte.

[0012] S4: Take 1-3 parts by weight of LITFSI, 2-6 parts by weight of polyethylene oxide (PEO), 50-150 parts by weight of acetonitrile, and 10-20 parts by weight of ionic liquid, mix them, and stir magnetically to obtain a pure PEO-based polymer mixture.

[0013] S5: The PEO-based polymer mixture is coated onto the other side of the LATP ceramic sheet by pressure coating and dried to obtain a polymer interface modified inorganic solid electrolyte.

[0014] The ionic liquid is a 1-allyl-3-butylimidazolium type ionic liquid.

[0015] Preferably, in step S1, the pre-firing temperature is 450-650℃, and the pre-firing time is 3-4 hours; the ball milling speed is 400-600 r / min, and the ball milling time is 8-10 hours; the pressing pressure is 250-350 MPa; and the selected powder is Li. 1.3 Al 0.3 Ti 1.7 (PO4)3 master powder; the sintering temperature of the embedded powder is 950-1050℃, and the sintering time of the embedded powder is 2-3h.

[0016] Preferably, in step S2, the mass fraction of PVDF-HFP is 3.8-34%, the mass fraction of LITFSI is 2.5-23%, and the mass fraction of inorganic solid electrolyte powder is 0.63-17%; the inorganic solid electrolyte powder is any one of LLZO, LATP, LGSP, LLTO, and LAGP.

[0017] Preferably, in step S2, the magnetic stirring speed is 300-400 r / min, the time is 16-24 h, and the temperature is 20-30℃.

[0018] Preferably, the drying temperature in step S3 is 60-80℃, the drying time is 6-20h, and the DMF mass fraction (relative to the PVDF-HFP polymer coating) after drying is 0.5%-5.0%.

[0019] Preferably, the PEO mass fraction (relative to the PEO polymer coating) in step S4 is 1.1%-9.5%, and the LITFSI mass fraction (relative to the PEO polymer coating) is 0.5%-4.8%.

[0020] Preferably, in step S4, the magnetic stirring speed is 350-400 r / min, the time is 16-24 h, and the temperature is 20-30℃.

[0021] Preferably, the drying temperature in step S5 is 20-30℃ and the drying time is 24-30h.

[0022] Based on a general inventive concept, embodiments of the present invention also provide a polymer interface modified inorganic solid electrolyte obtained by the above preparation method, which is a PVDF-HFP@LATP@PEO sandwich structure solid electrolyte; wherein, the thickness of the LATP ceramic sheet is less than 0.6 mm; the thickness of the PVDF-HFP based polymer film is 1-5 μm; and the thickness of the PEO based polymer film is 1-5 μm.

[0023] In another aspect, this invention provides the application of the polymer interface-modified inorganic solid electrolyte obtained by the above-described preparation method in a solid-state lithium battery. The polymer interface-modified inorganic solid electrolyte replaces the electrolyte and separator, and lithium metal is used as the negative electrode to assemble a coin cell. Preferably, a 2032 type coin cell is used.

[0024] The above-described solution of the present invention has the following beneficial effects:

[0025] (1) This invention uses a pressure coating method to coat an ionic liquid-type polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and polyoxyethylene (PEO) polymer mixture onto an LATP ceramic sheet to obtain a PVDF-HFP@LATP@PEO sandwich-structured solid electrolyte. Imidazole ionic liquids have good fluidity, effectively reducing the crystallinity of PEO and increasing its ionic conductivity and ion transference number. For the PVDF-HFP polymer mixture, it can effectively fix the position of the inorganic solid electrolyte powder during the evaporation and drying process, making it uniformly dispersed, reducing its own crystallinity, and improving electrochemical stability and mechanical strength, exhibiting excellent stability. The battery assembled with the prepared sandwich-structured solid electrolyte significantly improves the cycling performance at both room temperature and high temperature.

[0026] (2) PVDF-HFP with added ionic liquid can uniformly disperse inorganic ceramic powder during vacuum drying, effectively replacing the role of DMF solvent; PVDF-HFP with added inorganic ceramic powder can effectively improve its mechanical strength and ionic conductivity, while increasing the interfacial wettability between the positive electrode and LATP and reducing the interfacial impedance; retaining a small amount of DMF on the positive electrode side is beneficial to improving the ionic conductivity of the solid electrolyte and the battery charge and discharge performance.

[0027] (3) The addition of ionic liquid to PEO-based polymer can effectively improve the polymer's fluidity and mechanical strength, increase ionic conductivity, and inhibit the direct contact between LATP and lithium anode, thus inhibiting the growth of lithium dendrites; it can also effectively solve the problem of low ionic conductivity and lithium ion transference number at room temperature.

[0028] (4) The LATP ceramic sheet prepared by embedded powder sintering can improve its mechanical strength and inhibit lithium volatilization. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a SEM image of the PVDF-HFP-based polymer solid electrolyte on the positive electrode side of an embodiment of the present invention;

[0031] Figure 2 This is a SEM image of the PEO polymer solid electrolyte on the negative electrode side of an embodiment of the present invention. Detailed Implementation

[0032] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0033] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0035] This invention addresses existing problems by providing a polymer interface-modified inorganic solid electrolyte, its preparation method, and its application.

[0036] Example 1

[0037] A method for preparing a polymer interface-modified inorganic solid electrolyte includes the following steps:

[0038] 1) Li₂CO₃, Al₂O₃, TiO₂, and NH₄H₂PO₄ powders were weighed out in a molar ratio of 0.65:0.15:1.7:3, and pre-calcined (at 600℃ for 3 hours) to obtain Li 1.3 Al 0.3 Ti 1.7 (PO4) 3 blocks were ball-milled (speed 500 r / min, time 9 h) and then pressed under pressure of 300 MPa to obtain ceramic blanks. The blanks were sintered by embedding powder (temperature 1000℃, time 2 h) to obtain LATP ceramic sheets, which were then polished to make their thickness about 0.55 mm.

[0039] 2) Take 0.48g LITFSI in a glove box, add 5g DMF solvent, 0.72g PVDF-HFP, 0.12g LATP powder, and 0.4g 1-allyl-3-butylimidazolium ionic liquid in sequence, and stir magnetically at 400r / min for 24h to obtain PVDF-HFP based polymer mixture. Use sealing film to seal the gaps at the bottle mouth during stirring.

[0040] 3) A stainless steel sheet is held in place by a vacuum suction pen, and a PVDF-HFP-based polymer mixture is dipped into it. The mixture is then evenly coated onto one side of an LATP ceramic sheet using a pressure coating method to prepare a PVDF-HFP@LATP double-layer solid electrolyte membrane. The membrane is then vacuum dried at 80°C for 8 hours. The mass of the dried DMF accounts for 4.8% of the coating mass.

[0041] 4) Take 0.24g LITFSI in a glove box, add 15g acetonitrile solvent, 0.5g PEO powder and 0.25g 1-allyl-3-butylimidazolium ionic liquid in sequence, and stir magnetically at a stirring speed of 400r / min for 24h to obtain PEO-based polymer mixture. Use sealing film to seal the gap of the bottle mouth during stirring.

[0042] 5) Using a vacuum suction pen, one side of the stainless steel sheet is dipped into a PEO-based polymer mixture, which is then uniformly coated onto the other side of the LATP ceramic sheet using a pressure coating method to prepare a PVDF-HFP@LATP@PEO sandwich-structured solid electrolyte membrane. The membrane is then vacuum dried at 30℃ for 24 hours. The SEM image of the PVDF-HFP-based polymer solid electrolyte on the positive electrode side is shown below. Figure 1 SEM image of the PEO polymer solid electrolyte on the negative electrode side is shown below. Figure 2 .

[0043] 6) After uniformly mixing LiCoO2 (80wt%), PVDF (10wt%), SuperP (10wt%), and an appropriate amount of NMP, the positive electrode sheet was obtained through slurry preparation, coating, drying, and cutting. A solid-state battery was assembled using lithium metal as the negative electrode, a sandwich solid electrolyte instead of the electrolyte, and a separator. Under 25℃ conditions, the battery exhibited a voltage range of 2.8-4.2V. Charge-discharge tests were conducted at a current density of 0.2C. The initial discharge specific capacity was 145.85 mAh / g, and the capacity retention rate after 50 cycles was 85.7%.

[0044] Example 2

[0045] A method for preparing a polymer interface-modified inorganic solid electrolyte includes the following steps:

[0046] 1) Li₂CO₃, Al₂O₃, TiO₂, and NH₄H₂PO₄ powders were weighed out in a molar ratio of 0.65:0.15:1.7:3, and pre-calcined (at 600℃ for 3 hours) to obtain Li 1.3 Al 0.3 Ti 1.7 (PO4) 3 blocks were ball-milled (speed 500 r / min, time 9 h) and then pressed under pressure of 300 MPa to obtain ceramic blanks. The blanks were sintered by embedding powder (temperature 1000℃, time 2 h) to obtain LATP ceramic sheets, which were then polished to make their thickness about 0.55 mm.

[0047] 2) Take 0.48g LITFSI in a glove box, add 5g DMF solvent, 0.72g PVDF-HFP, 0.12g LATP powder, and 0.4g 1-allyl-3-butylimidazolium ionic liquid in sequence, and stir magnetically at 400r / min for 24h to obtain PVDF-HFP based polymer mixture. Use sealing film to seal the gaps at the bottle mouth during stirring.

[0048] 3) A stainless steel sheet is held in place by a vacuum suction pen, and a PVDF-HFP-based polymer mixture is dipped into it. The mixture is then evenly coated onto one side of an LATP ceramic sheet using a pressure coating method to prepare a PVDF-HFP@LATP double-layer solid electrolyte membrane. The membrane is then vacuum dried at 80°C for 8 hours. The mass of the dried DMF accounts for 4.8% of the coating mass.

[0049] 4) Take 0.24g LITFSI in a glove box, add 15g acetonitrile solvent, 0.5g PEO powder and 0.25g 1-allyl-3-butylimidazolium ionic liquid in sequence, and stir magnetically at a stirring speed of 400r / min for 24h to obtain PEO-based polymer mixture. Use sealing film to seal the gap of the bottle mouth during stirring.

[0050] 5) Hold one side of the stainless steel sheet with a vacuum suction pen, dip it into the PEO-based polymer mixture, and evenly coat it onto the other side of the LATP ceramic sheet by pressure coating to prepare a PVDF-HFP@LATP@PEO sandwich structure solid electrolyte membrane. Then, vacuum dry it at a temperature of 30°C for 24 hours.

[0051] 6) After uniformly mixing LiCoO2 (80wt%), PVDF (10wt%), SuperP (10wt%), and an appropriate amount of NMP, the positive electrode sheet was obtained through slurry preparation, coating, drying, and cutting. A solid-state battery was assembled using lithium metal as the negative electrode, a sandwich solid electrolyte instead of the electrolyte, and a separator. Under conditions of 60℃, the battery exhibited a voltage range of 2.8-4.2V and under a charge-discharge test at a current density of 0.2C. The initial discharge specific capacity was 136.87mAh / g, and the capacity retention rate after 50 cycles was 79.78%.

[0052] Example 3

[0053] A method for preparing a polymer interface-modified inorganic solid electrolyte includes the following steps:

[0054] 1) Li₂CO₃, Al₂O₃, TiO₂, and NH₄H₂PO₄ powders were weighed out in a molar ratio of 0.65:0.15:1.7:3, and pre-calcined (at 600℃ for 3 hours) to obtain Li 1.3 Al 0.3 Ti 1.7 (PO4) 3 blocks were ball-milled (speed 500 r / min, time 9 h) and then pressed under pressure of 300 MPa to obtain ceramic blanks. The blanks were sintered by embedding powder (temperature 1000℃, time 2 h) to obtain LATP ceramic sheets, which were then polished to make their thickness about 0.55 mm.

[0055] 2) Take 0.48g LITFSI in a glove box, add 5g DMF solvent, 0.72g PVDF-HFP, 0.12g LATP powder, and 0.4g 1-allyl-3-butylimidazolium ionic liquid in sequence, and stir magnetically at 400r / min for 24h to obtain PVDF-HFP based polymer mixture. Use sealing film to seal the gaps at the bottle mouth during stirring.

[0056] 3) A stainless steel sheet is held in place by a vacuum suction pen, and a PVDF-HFP-based polymer mixture is dipped into it. The mixture is then evenly coated onto one side of an LATP ceramic sheet using a pressure coating method to prepare a PVDF-HFP@LATP double-layer solid electrolyte membrane. The membrane is then vacuum dried at 80°C for 8 hours. The mass of the dried DMF accounts for 4.8% of the coating mass.

[0057] 4) Take 0.24g LITFSI in a glove box, add 15g acetonitrile solvent, 0.5g PEO powder and 0.25g 1-allyl-3-butylimidazolium ionic liquid in sequence, and stir magnetically at a stirring speed of 400r / min for 24h to obtain PEO-based polymer mixture. Use sealing film to seal the gap of the bottle mouth during stirring.

[0058] 5) Hold one side of the stainless steel sheet with a vacuum suction pen, dip it into the PEO-based polymer mixture, and evenly coat it onto the other side of the LATP ceramic sheet by pressure coating to prepare a PVDF-HFP@LATP@PEO sandwich structure solid electrolyte membrane. Then, vacuum dry it at a temperature of 30°C for 24 hours.

[0059] 6) After uniformly mixing LiFePO4 (80wt%), PVDF (10wt%), SuperP (10wt%), and an appropriate amount of NMP, the positive electrode sheet was obtained through slurry preparation, coating, drying, and cutting. A solid-state battery was assembled using lithium metal as the negative electrode, a sandwich solid electrolyte instead of the electrolyte, and a separator. Under 25℃ conditions, the battery exhibited a voltage range of 2.5-4.1V and under a charge-discharge test at a current density of 0.2C. The initial discharge specific capacity was 150.67mAh / g, and the capacity retention rate after 50 cycles was 94.35%.

[0060] Example 4

[0061] A method for preparing a polymer interface-modified inorganic solid electrolyte includes the following steps:

[0062] 1) Li₂CO₃, Al₂O₃, TiO₂, and NH₄H₂PO₄ powders were weighed out in a molar ratio of 0.65:0.15:1.7:3, and pre-calcined (at 600℃ for 3 hours) to obtain Li 1.3 Al 0.3 Ti 1.7 (PO4) 3 blocks were ball-milled (speed 500 r / min, time 9 h) and then pressed under pressure of 300 MPa to obtain ceramic blanks. The blanks were sintered by embedding powder (temperature 1000℃, time 2 h) to obtain LATP ceramic sheets, which were then polished to make their thickness about 0.55 mm.

[0063] 2) Take 0.48g LITFSI in a glove box, add 5g DMF solvent, 0.72g PVDF-HFP, 0.12g LATP powder, and 0.4g 1-allyl-3-butylimidazolium ionic liquid in sequence, and stir magnetically at 400r / min for 24h to obtain PVDF-HFP based polymer mixture. Use sealing film to seal the gaps at the bottle mouth during stirring.

[0064] 3) A stainless steel sheet is held in place by a vacuum suction pen, and a PVDF-HFP-based polymer mixture is dipped into it. The mixture is then evenly coated onto one side of an LATP ceramic sheet using a pressure coating method to prepare a PVDF-HFP@LATP double-layer solid electrolyte membrane. The membrane is then vacuum dried at 80°C for 8 hours. The mass of the dried DMF accounts for 4.8% of the coating mass.

[0065] 4) Take 0.24g LITFSI in a glove box, add 15g acetonitrile solvent, 0.5g PEO powder and 0.25g 1-allyl-3-butylimidazolium ionic liquid in sequence, and stir magnetically at a stirring speed of 400r / min for 24h to obtain PEO-based polymer mixture. Use sealing film to seal the gap of the bottle mouth during stirring.

[0066] 5) Hold one side of the stainless steel sheet with a vacuum suction pen, dip it into the PEO-based polymer mixture, and evenly coat it onto the other side of the LATP ceramic sheet by pressure coating to prepare a PVDF-HFP@LATP@PEO sandwich structure solid electrolyte membrane. Then, vacuum dry it at a temperature of 30°C for 24 hours.

[0067] 6) After uniformly mixing LiFePO4 (80wt%), PVDF (10wt%), SuperP (10wt%), and an appropriate amount of NMP, the positive electrode sheet was obtained through slurry preparation, coating, drying, and cutting. A solid-state battery was assembled using lithium metal as the negative electrode and a sandwich solid electrolyte instead of the electrolyte and separator. Under conditions of 60℃, the battery exhibited a voltage range of 2.5-4.1V and under a charge-discharge test at a current density of 0.2C. The initial discharge specific capacity was 144.32 mAh / g, and the capacity retention rate after 50 cycles was 81.78%.

[0068] As can be seen from Examples 1 to 4, the prepared PVDF-HFP@LATP@PEO sandwich structure solid electrolyte assembled battery has a wide range of cathode material adaptability.

[0069] Comparative Example 1

[0070] In step 2 of Example 1, no ionic liquid was added, and the other steps were the same as in Example 1. The resulting sandwich-structured solid electrolyte was assembled into a battery. Under conditions of 25°C, the battery exhibited a voltage range of 2.8-4.2V and was tested for charge and discharge at a current density of 0.2C. The initial discharge specific capacity of the battery was 124.26 mAh / g, and the capacity retention rate after 50 cycles was 40.64%.

[0071] Comparative Example 2

[0072] In step 4 of Example 1, no ionic liquid was added; the other steps were the same as in Example 1. The resulting sandwich-structured solid electrolyte was assembled into a battery. Under conditions of 25°C, the battery exhibited a voltage range of 2.8-4.2V and was tested for charge and discharge at a current density of 0.2C. The initial discharge specific capacity of the battery was 85.34 mAh / g, and the capacity retention rate after 50 cycles was 30.87%.

[0073] Comparative Example 3

[0074] In Example 1, steps 2 and 4 were performed without adding ionic liquid, while the other steps were the same as in Example 1. The resulting sandwich-structured solid electrolyte was then assembled into a battery. Under conditions of 25°C, the battery exhibited a voltage range of 2.8-4.2V and under charge-discharge testing at a current density of 0.2C. The initial discharge specific capacity of the battery was 30.25 mAh / g, and the capacity retention rate after 50 cycles was 8.74%.

[0075] Comparative Example 4

[0076] In step 2 of Example 2, no ionic liquid was added, and the other steps were the same as in Example 2. The resulting sandwich-structured solid electrolyte was assembled into a battery. Under conditions of 60°C, the battery exhibited a voltage range of 2.8-4.2V and was tested for charge and discharge at a current density of 0.2C. The initial discharge specific capacity was 75.23 mAh / g, and the capacity retention rate after 50 cycles was 20.67%.

[0077] Comparative Example 5

[0078] In step 4 of Example 2, no ionic liquid was added, while the other steps were the same as in Example 2. The resulting sandwich-structured solid electrolyte was assembled into a battery. Under conditions of 60°C, with a voltage range of 2.8-4.2V, and after charge-discharge testing at a current density of 0.2C, the battery exhibited an initial discharge specific capacity of 67.81 mAh / g and a capacity retention rate of 22.53% after 50 cycles.

[0079] Comparative Example 6

[0080] In Example 2, steps 2 and 4 were performed without adding ionic liquid, while the other steps were the same as in Example 2. The resulting sandwich-structured solid electrolyte was then assembled into a battery. Under conditions of 60°C, with a voltage range of 2.8-4.2V, and after charge-discharge testing at a current density of 0.2C, the battery exhibited an initial discharge specific capacity of 52.87 mAh / g and a capacity retention rate of 10.89% after 50 cycles.

[0081] Comparative Example 7 (The drying time in step 3 of Example 1 was modified, resulting in a different DMF content on the positive electrode side compared to Example 1, while other aspects remained unchanged)

[0082] A method for preparing a polymer interface-modified inorganic solid electrolyte includes the following steps:

[0083] 1) Li₂CO₃, Al₂O₃, TiO₂, and NH₄H₂PO₄ powders were weighed out in a molar ratio of 0.65:0.15:1.7:3, and pre-calcined (at 600℃ for 3 hours) to obtain Li 1.3 Al 0.3 Ti 1.7 (PO4) 3 blocks were ball-milled (speed 500 r / min, time 9 h) and then pressed under pressure of 300 MPa to obtain ceramic blanks. The blanks were sintered by embedding powder (temperature 1000℃, time 2 h) to obtain LATP ceramic sheets, which were then polished to make their thickness about 0.55 mm.

[0084] 2) Take 0.48g LITFSI in a glove box, add 5g DMF solvent, 0.72g PVDF-HFP, 0.12g LATP powder, and 0.4g 1-allyl-3-butylimidazolium ionic liquid in sequence, and stir magnetically at 400r / min for 24h to obtain PVDF-HFP based polymer mixture. Use sealing film to seal the gaps at the bottle mouth during stirring.

[0085] 3) A stainless steel sheet is held in place by a vacuum suction pen, and a PVDF-HFP-based polymer mixture is dipped into it. The mixture is then evenly coated onto one side of an LATP ceramic sheet using a pressure coating method to prepare a PVDF-HFP@LATP double-layer solid electrolyte membrane. The membrane is then vacuum dried at 80°C for 18 hours. The mass of the dried DMF accounts for 0.23% of the coating mass.

[0086] 4) Take 0.24g LITFSI in a glove box, add 15g acetonitrile solvent, 0.5g PEO powder and 0.25g 1-allyl-3-butylimidazolium ionic liquid in sequence, and stir magnetically at a stirring speed of 400r / min for 24h to obtain PEO-based polymer mixture. Use sealing film to seal the gap of the bottle mouth during stirring.

[0087] 5) Hold one side of the stainless steel sheet with a vacuum suction pen, dip it into the PEO-based polymer mixture, and evenly coat it onto the other side of the LATP ceramic sheet by pressure coating to prepare a PVDF-HFP@LATP@PEO sandwich structure solid electrolyte membrane. Then, vacuum dry it at a temperature of 30°C for 24 hours.

[0088] 6) After uniformly mixing LiCoO2 (80wt%), PVDF (10wt%), SuperP (10wt%), and an appropriate amount of NMP, the positive electrode sheet was obtained through slurry preparation, coating, drying, and cutting. A solid-state battery was assembled using lithium metal as the negative electrode, a sandwich solid electrolyte instead of the electrolyte, and a separator. Under 25℃ conditions, the battery exhibited a voltage range of 2.5-4.1V and under a charge-discharge test at a current density of 0.2C. The initial discharge specific capacity was 100.67mAh / g, and the capacity retention rate after 50 cycles was 45.27%.

[0089] Comparative Example 8 (The drying time in step 3 of Example 2 was modified, resulting in a different DMF content on the positive electrode side compared to Example 1, while other aspects remained unchanged)

[0090] A method for preparing a polymer interface-modified inorganic solid electrolyte includes the following steps:

[0091] 1) Li₂CO₃, Al₂O₃, TiO₂, and NH₄H₂PO₄ powders were weighed out in a molar ratio of 0.65:0.15:1.7:3, and pre-calcined (at 600℃ for 3 hours) to obtain Li 1.3 Al 0.3 Ti 1.7 (PO4) 3 blocks were ball-milled (speed 500 r / min, time 9 h) and then pressed under pressure of 300 MPa to obtain ceramic blanks. The blanks were sintered by embedding powder (temperature 1000℃, time 2 h) to obtain LATP ceramic sheets, which were then polished to make their thickness about 0.55 mm.

[0092] 2) Take 0.48g LITFSI in a glove box, add 5g DMF solvent, 0.72g PVDF-HFP, 0.12g LATP powder, and 0.4g 1-allyl-3-butylimidazolium ionic liquid in sequence, and stir magnetically at 400r / min for 24h to obtain PVDF-HFP based polymer mixture. Use sealing film to seal the gaps at the bottle mouth during stirring.

[0093] 3) A stainless steel sheet is held in place by a vacuum suction pen, and a PVDF-HFP-based polymer mixture is dipped into it. The mixture is then evenly coated onto one side of an LATP ceramic sheet using a pressure coating method to prepare a PVDF-HFP@LATP double-layer solid electrolyte membrane. The membrane is then vacuum dried at 80°C for 18 hours. The mass of the dried DMF accounts for 0.23% of the coating mass.

[0094] 4) Take 0.24g LITFSI in a glove box, add 15g acetonitrile solvent, 0.5g PEO powder and 0.25g 1-allyl-3-butylimidazolium ionic liquid in sequence, and stir magnetically at a stirring speed of 400r / min for 24h to obtain PEO-based polymer mixture. Use sealing film to seal the gap of the bottle mouth during stirring.

[0095] 5) Hold one side of the stainless steel sheet with a vacuum suction pen, dip it into the PEO-based polymer mixture, and evenly coat it onto the other side of the LATP ceramic sheet by pressure coating to prepare a PVDF-HFP@LATP@PEO sandwich structure solid electrolyte membrane. Then, vacuum dry it at a temperature of 30°C for 24 hours.

[0096] 6) After uniformly mixing LiCoO2 (80wt%), PVDF (10wt%), SuperP (10wt%), and an appropriate amount of NMP, the positive electrode sheet was obtained through slurry preparation, coating, drying, and cutting. A solid-state battery was assembled using lithium metal as the negative electrode and a sandwich solid electrolyte instead of the electrolyte and separator. Under conditions of 60℃, the battery exhibited a voltage range of 2.5-4.1V and under a charge-discharge test at a current density of 0.2C. The initial discharge specific capacity was 115.32 mAh / g, and the capacity retention rate after 50 cycles was 23.14%.

[0097] As can be seen from Comparative Examples 7 and 8, retaining a small amount of DMF on the positive electrode side, with a mass fraction (relative to PVDF-HFP) of 1%-5%, is beneficial to improving the ionic conductivity of the solid electrolyte and the battery charge-discharge performance.

[0098] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a polymer interface-modified inorganic solid electrolyte, characterized in that, Includes the following steps: S1: Li₂CO₃, Al₂O₃, TiO₂, and NH₄H₂PO₄ powders were weighed out in a molar ratio of 0.65:0.15:1.7:3, and then pre-calcined to obtain Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is ball-milled and pressed to obtain a ceramic blank, which is then sintered by embedding powder and polished to obtain LATP ceramic sheet; S2: Take 1-3 parts by weight of inorganic solid electrolyte powder, 4-12 parts by weight of LITFSI, 6-18 parts by weight of PVDF-HFP, 40-120 parts by weight of DMF, and 2-6 parts by weight of ionic liquid, mix them, and stir magnetically to obtain a PVDF-HFP based polymer mixture. S3: The PVDF-HFP based polymer mixture is coated onto the LATP ceramic sheet by pressure coating and then dried by vacuum evaporation to obtain the PVDF-HFP@LATP bilayer solid electrolyte. S4: Mix 0.24g LITFSI, 0.5g PEO, 15g acetonitrile, and 0.25g ionic liquid, and stir magnetically to obtain a pure PEO-based polymer mixture; S5: The PEO-based polymer mixture is coated onto the other side of the LATP ceramic sheet by pressure coating and dried to obtain a polymer interface modified inorganic solid electrolyte. The ionic liquid is a 1-allyl-3-butylimidazolium type ionic liquid.

2. The preparation method according to claim 1, characterized in that, The pre-firing temperature in step S1 is 450-650℃, and the pre-firing time is 3-4 hours; the ball milling speed is 400-600 r / min, and the ball milling time is 8-10 hours; the pressing pressure is 250-350 MPa; and the Li powder used is... 1.3 Al 0.3 Ti 1.7 (PO4)3 master powder; the sintering temperature of the embedded powder is 950-1050℃, and the sintering time of the embedded powder is 2-3h.

3. The preparation method according to claim 2, characterized in that, In step S2, the PVDF-HFP mass fraction is 3.8-34%, the LITFSI mass fraction is 2.5-23%, and the inorganic solid electrolyte powder mass fraction is 0.63-17%; the inorganic solid electrolyte powder is any one of LLZO, LATP, LGSP, LLTO, and LAGP.

4. The preparation method according to claim 3, characterized in that, In step S2, the magnetic stirring speed is 300-400 r / min, the time is 16-24 h, and the temperature is 20-30℃.

5. The preparation method according to claim 4, characterized in that, The drying temperature in step S3 is 60-80℃, the drying time is 6-20h, and the mass fraction of DMF relative to the dried PVDF-HFP polymer coating is 0.5%-5.0%.

6. The preparation method according to claim 1, characterized in that, In S4, the magnetic stirring speed is 350-400 r / min, the time is 16-24 h, and the temperature is 20-30℃.

7. The preparation method according to claim 1, characterized in that, The drying temperature in S5 is 20-30℃, and the drying time is 24-30h.

8. The polymer interface-modified inorganic solid electrolyte obtained by the preparation method according to any one of claims 1 to 7, characterized in that, It is a PVDF-HFP@LATP@PEO sandwich structure solid electrolyte; wherein, the thickness of the LATP ceramic sheet is less than 0.6 mm; the thickness of the PVDF-HFP based polymer film is 1-5 μm; and the thickness of the PEO based polymer film is 1-5 μm.

9. The application of the polymer interface-modified inorganic solid electrolyte obtained by the preparation method according to any one of claims 1 to 7 in solid-state lithium batteries, characterized in that, The polymer interface-modified inorganic solid electrolyte replaces the electrolyte and separator, and lithium metal is used as the negative electrode to assemble a coin cell.

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